ASoC: qcom: add dma channel control offset to variant data

This patch adds ability to pass dma channel control bits start offset,
which differ in differnet qcom SOCs. On apq8016 dma channel control bits
start after an offset of 1.

Tested-by: Kenneth Westfield <kwestfie@codeaurora.org>
Acked-by: Kenneth Westfield <kwestfie@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>